info -
Return information about the state of the Tcl interpreter
info option ?arg arg ...?
This command provides information about various internals of the Tcl
interpreter.
The legal options (which may be abbreviated) are:
-
info args procname
- Returns a list containing the names of the arguments to procedure
procname, in order. Procname must be the name of a
Tcl command procedure.
-
info body procname
- Returns the body of procedure procname. Procname must be
the name of a Tcl command procedure.
-
info class subcommand class ?arg ...
- Returns information about the class, class. The subcommands are
described in CLASS INTROSPECTION below.
- info cmdcount
- Returns a count of the total number of commands that have been invoked
in this interpreter.
-
info commands ?pattern?
- If pattern is not specified,
returns a list of names of all the Tcl commands visible
(i.e. executable without using a qualified name) to the current namespace,
including both the built-in commands written in C and
the command procedures defined using the proc command.
If pattern is specified,
only those names matching pattern are returned.
Matching is determined using the same rules as for string match.
pattern can be a qualified name like Foo::print*.
That is, it may specify a particular namespace
using a sequence of namespace names separated by double colons (::),
and may have pattern matching special characters
at the end to specify a set of commands in that namespace.
If pattern is a qualified name,
the resulting list of command names has each one qualified with the name
of the specified namespace, and only the commands defined in the named
namespace are returned.
-
info complete command
- Returns 1 if command is a complete Tcl command in the sense of
having no unclosed quotes, braces, brackets or array element names.
If the command does not appear to be complete then 0 is returned.
This command is typically used in line-oriented input environments
to allow users to type in commands that span multiple lines; if the
command is not complete, the script can delay evaluating it until additional
lines have been typed to complete the command.
- info coroutine
- Returns the name of the currently executing coroutine, or the empty
string if either no coroutine is currently executing, or the current coroutine
has been deleted (but has not yet returned or yielded since deletion).
-
info default procname arg varname
-
Procname must be the name of a Tcl command procedure and arg
must be the name of an argument to that procedure. If arg
does not have a default value then the command returns 0.
Otherwise it returns 1 and places the default value of arg
into variable varname.
-
info errorstack ?interp?
-
Returns, in a form that is programmatically easy to parse, the function names
and arguments at each level from the call stack of the last error in the given
interp, or in the current one if not specified.
This form is an even-sized list alternating tokens and parameters. Tokens are
currently either CALL, UP, or INNER, but other values may be
introduced in the future. CALL indicates a procedure call, and its
parameter is the corresponding info level 0. UP indicates a
shift in variable frames generated by uplevel or similar, and applies to
the previous CALL item. Its parameter is the level offset. INNER
identifies the
"inner context", which is the innermost atomic command or bytecode instruction that raised the
error, along with its arguments when available. While CALL and UP
allow to follow complex call paths, INNER homes in on the offending
operation in the innermost procedure call, even going to sub-expression
granularity.
This information is also present in the -errorstack entry of the
options dictionary returned by 3-argument catch; info errorstack
is a convenient way of retrieving it for uncaught errors at top-level in an
interactive tclsh.
-
info exists varName
- Returns 1 if the variable named varName exists in the
current context (either as a global or local variable) and has been
defined by being given a value, returns 0 otherwise.
-
info frame ?number?
- This command provides access to all frames on the stack, even those
hidden from info level. If number is not specified, this
command returns a number giving the frame level of the command. This
is 1 if the command is invoked at top-level. If number is
specified, then the result is a dictionary containing the location
information for the command at the numbered level on the stack.
If number is positive (> 0) then it selects a particular stack
level (1 refers to the outer-most active command, 2 to the command it
called, and so on, up to the current frame level which refers to
info frame itself); otherwise it gives a level relative to the
current command (0 refers to the current command, i.e., info
frame itself, -1 to its caller, and so on).
This is similar to how info level works, except that this
subcommand reports all frames, like sourced scripts,
evals, uplevels, etc.
Note that for nested commands, like
"foo [bar [x]]", only
"x" will be seen by an info frame invoked within
"x". This is the same as for info level and error stack traces.
The result dictionary may contain the keys listed below, with the
specified meanings for their values:
- type
- This entry is always present and describes the nature of the location
for the command. The recognized values are source, proc,
eval, and precompiled.
-
source
- means that the command is found in a script loaded by the source
command.
-
proc
- means that the command is found in dynamically created procedure body.
-
eval
- means that the command is executed by eval or uplevel.
-
precompiled
- means that the command is found in a pre-compiled script (loadable by
the package tbcload), and no further information will be
available.
- line
- This entry provides the number of the line the command is at inside of
the script it is a part of. This information is not present for type
precompiled. For type source this information is counted
relative to the beginning of the file, whereas for the last two types
the line is counted relative to the start of the script.
- file
- This entry is present only for type source. It provides the
normalized path of the file the command is in.
- cmd
- This entry provides the string representation of the command. This is
usually the unsubstituted form, however for commands which are a
canonically-constructed list (e.g., as produced by the list command)
executed by eval it is the substituted form as they have no other
string representation. Care is taken that the canonicality property of
the latter is not spoiled.
- proc
- This entry is present only if the command is found in the body of a
regular Tcl procedure. It then provides the name of that procedure.
- lambda
- This entry is present only if the command is found in the body of an
anonymous Tcl procedure, i.e. a lambda. It then provides the entire
definition of the lambda in question.
- level
- This entry is present only if the queried frame has a corresponding
frame returned by info level. It provides the index of this
frame, relative to the current level (0 and negative numbers).
A thing of note is that for procedures statically defined in files the
locations of commands in their bodies will be reported with type
source and absolute line numbers, and not as type
proc. The same is true for procedures nested in statically
defined procedures, and literal eval scripts in files or statically
defined procedures.
In contrast, procedure definitions and eval within a dynamically
evaluated environment count line numbers relative to the start of
their script, even if they would be able to count relative to the
start of the outer dynamic script. That type of number usually makes
more sense.
A different way of describing this behaviour is that file based
locations are tracked as deeply as possible, and where this is not
possible the lines are counted based on the smallest possible
eval or procedure body, as that scope is usually easier to find
than any dynamic outer scope.
The syntactic form {*} is handled like eval. I.e. if it
is given a literal list argument the system tracks the line number
within the list words as well, and otherwise all line numbers are
counted relative to the start of each word (smallest scope)
-
info functions ?pattern?
- If pattern is not specified, returns a list of all the math
functions currently defined.
If pattern is specified, only those functions whose name matches
pattern are returned. Matching is determined using the same
rules as for string match.
-
info globals ?pattern?
- If pattern is not specified, returns a list of all the names
of currently-defined global variables.
Global variables are variables in the global namespace.
If pattern is specified, only those names matching pattern
are returned. Matching is determined using the same rules as for
string match.
- info hostname
- Returns the name of the computer on which this invocation is being
executed.
Note that this name is not guaranteed to be the fully qualified domain
name of the host. Where machines have several different names (as is
common on systems with both TCP/IP (DNS) and NetBIOS-based networking
installed,) it is the name that is suitable for TCP/IP networking that
is returned.
-
info level ?number?
- If number is not specified, this command returns a number
giving the stack level of the invoking procedure, or 0 if the
command is invoked at top-level. If number is specified,
then the result is a list consisting of the name and arguments for the
procedure call at level number on the stack. If number
is positive then it selects a particular stack level (1 refers
to the top-most active procedure, 2 to the procedure it called, and
so on); otherwise it gives a level relative to the current level
(0 refers to the current procedure, -1 to its caller, and so on).
See the uplevel command for more information on what stack
levels mean.
- info library
- Returns the name of the library directory in which standard Tcl
scripts are stored.
This is actually the value of the tcl_library
variable and may be changed by setting tcl_library.
See the tclvars manual entry for more information.
-
info loaded ?interp?
- Returns a list describing all of the packages that have been loaded into
interp with the load command.
Each list element is a sub-list with two elements consisting of the
name of the file from which the package was loaded and the name of
the package.
For statically-loaded packages the file name will be an empty string.
If interp is omitted then information is returned for all packages
loaded in any interpreter in the process.
To get a list of just the packages in the current interpreter, specify
an empty string for the interp argument.
-
info locals ?pattern?
- If pattern is not specified, returns a list of all the names
of currently-defined local variables, including arguments to the
current procedure, if any.
Variables defined with the global, upvar and
variable commands will not be returned.
If pattern is specified, only those names matching pattern
are returned. Matching is determined using the same rules as for
string match.
- info nameofexecutable
- Returns the full path name of the binary file from which the application
was invoked. If Tcl was unable to identify the file, then an empty
string is returned.
-
info object subcommand object ?arg ...
- Returns information about the object, object. The subcommands are
described in OBJECT INTROSPECTION below.
- info patchlevel
- Returns the value of the global variable tcl_patchLevel; see
the tclvars manual entry for more information.
-
info procs ?pattern?
- If pattern is not specified, returns a list of all the
names of Tcl command procedures in the current namespace.
If pattern is specified,
only those procedure names in the current namespace
matching pattern are returned.
Matching is determined using the same rules as for
string match.
If pattern contains any namespace separators, they are used to
select a namespace relative to the current namespace (or relative to
the global namespace if pattern starts with ::) to match
within; the matching pattern is taken to be the part after the last
namespace separator.
-
info script ?filename?
- If a Tcl script file is currently being evaluated (i.e. there is a
call to Tcl_EvalFile active or there is an active invocation
of the source command), then this command returns the name
of the innermost file being processed. If filename is specified,
then the return value of this command will be modified for the
duration of the active invocation to return that name. This is
useful in virtual file system applications.
Otherwise the command returns an empty string.
- info sharedlibextension
- Returns the extension used on this platform for the names of files
containing shared libraries (for example, .so under Solaris).
If shared libraries are not supported on this platform then an empty
string is returned.
- info tclversion
- Returns the value of the global variable tcl_version; see
the tclvars manual entry for more information.
-
info vars ?pattern?
- If pattern is not specified,
returns a list of all the names of currently-visible variables.
This includes locals and currently-visible globals.
If pattern is specified, only those names matching pattern
are returned. Matching is determined using the same rules as for
string match.
pattern can be a qualified name like Foo::option*.
That is, it may specify a particular namespace
using a sequence of namespace names separated by double colons (::),
and may have pattern matching special characters
at the end to specify a set of variables in that namespace.
If pattern is a qualified name,
the resulting list of variable names
has each matching namespace variable qualified with the name
of its namespace.
Note that a currently-visible variable may not yet
"exist" if it has not
been set (e.g. a variable declared but not set by variable).
The following subcommand values are supported by info class:
-
info class call class method
-
Returns a description of the method implementations that are used to provide a
stereotypical instance of class's implementation of method
(stereotypical instances being objects instantiated by a class without having
any object-specific definitions added). This consists of a list of lists of
four elements, where each sublist consists of a word that describes the
general type of method implementation (being one of method for an
ordinary method, filter for an applied filter, and unknown for a
method that is invoked as part of unknown method handling), a word giving the
name of the particular method invoked (which is always the same as
method for the method type, and
"unknown" for the unknown type), a word giving the fully qualified name of the
class that defined the method, and a word describing the type of method
implementation (see info class methodtype).
Note that there is no inspection of whether the method implementations
actually use next to transfer control along the call chain.
-
info class constructor class
- This subcommand returns a description of the definition of the constructor of
class class. The definition is described as a two element list; the first
element is the list of arguments to the constructor in a form suitable for
passing to another call to proc or a method definition, and the second
element is the body of the constructor. If no constructor is present, this
returns the empty list.
-
info class definition class method
- This subcommand returns a description of the definition of the method named
method of class class. The definition is described as a two element
list; the first element is the list of arguments to the method in a form
suitable for passing to another call to proc or a method definition, and
the second element is the body of the method.
-
info class destructor class
- This subcommand returns the body of the destructor of class class. If no
destructor is present, this returns the empty string.
-
info class filters class
- This subcommand returns the list of filter methods set on the class.
-
info class forward class method
- This subcommand returns the argument list for the method forwarding called
method that is set on the class called class.
-
info class instances class ?pattern?
- This subcommand returns a list of instances of class class. If the
optional pattern argument is present, it constrains the list of returned
instances to those that match it according to the rules of string match.
-
info class methods class ?options...?
- This subcommand returns a list of all public (i.e. exported) methods of the
class called class. Any of the following options may be
specified, controlling exactly which method names are returned:
- -all
- If the -all flag is given, the list of methods will include those
methods defined not just by the class, but also by the class's superclasses
and mixins.
- -private
-
If the -private flag is given, the list of methods will also include
the private (i.e. non-exported) methods of the class (and superclasses and
mixins, if -all is also given).
-
info class methodtype class method
- This subcommand returns a description of the type of implementation used for
the method named method of class class. When the result is
method, further information can be discovered with info class
definition, and when the result is forward, further information can
be discovered with info class forward.
-
info class mixins class
- This subcommand returns a list of all classes that have been mixed into the
class named class.
-
info class subclasses class ?pattern?
- This subcommand returns a list of direct subclasses of class class. If
the optional pattern argument is present, it constrains the list of
returned classes to those that match it according to the rules of
string match.
-
info class superclasses class
- This subcommand returns a list of direct superclasses of class class in
inheritance precedence order.
-
info class variables class
-
This subcommand returns a list of all variables that have been declared for
the class named class (i.e. that are automatically present in the
class's methods, constructor and destructor).
The following subcommand values are supported by info object:
-
info object call object method
-
Returns a description of the method implementations that are used to provide
object's implementation of method. This consists of a list of
lists of four elements, where each sublist consists of a word that describes
the general type of method implementation (being one of method for an
ordinary method, filter for an applied filter, and unknown for a
method that is invoked as part of unknown method handling), a word giving the
name of the particular method invoked (which is always the same as
method for the method type, and
"unknown" for the unknown type), a word giving what defined the method (the fully
qualified name of the class, or the literal string object if the method
implementation is on an instance), and a word describing the type of method
implementation (see info object methodtype).
Note that there is no inspection of whether the method implementations
actually use next to transfer control along the call chain.
-
info object class object ?className?
- If className is unspecified, this subcommand returns class of the
object object. If className is present, this subcommand returns a
boolean value indicating whether the object is of that class.
-
info object definition object method
- This subcommand returns a description of the definition of the method named
method of object object. The definition is described as a two
element list; the first element is the list of arguments to the method in a
form suitable for passing to another call to proc or a method definition,
and the second element is the body of the method.
-
info object filters object
- This subcommand returns the list of filter methods set on the object.
-
info object forward object method
- This subcommand returns the argument list for the method forwarding called
method that is set on the object called object.
-
info object isa category object ?arg?
- This subcommand tests whether an object belongs to a particular category,
returning a boolean value that indicates whether the object argument
meets the criteria for the category. The supported categories are:
-
info object isa class object
- This returns whether object is a class (i.e. an instance of
oo::class or one of its subclasses).
-
info object isa metaclass object
- This returns whether object is a class that can manufacture classes
(i.e. is oo::class or a subclass of it).
-
info object isa mixin object class
- This returns whether class is directly mixed into object.
-
info object isa object object
- This returns whether object really is an object.
-
info object isa typeof object class
-
This returns whether class is the type of object (i.e. whether
object is an instance of class or one of its subclasses, whether
direct or indirect).
-
info object methods object ?option...?
- This subcommand returns a list of all public (i.e. exported) methods of the
object called object. Any of the following options may be
specified, controlling exactly which method names are returned:
- -all
- If the -all flag is given, the list of methods will include those
methods defined not just by the object, but also by the object's class and
mixins, plus the superclasses of those classes.
- -private
-
If the -private flag is given, the list of methods will also include
the private (i.e. non-exported) methods of the object (and classes, if
-all is also given).
-
info object methodtype object method
- This subcommand returns a description of the type of implementation used for
the method named method of object object. When the result is
method, further information can be discovered with info object
definition, and when the result is forward, further information can
be discovered with info object forward.
-
info object mixins object
- This subcommand returns a list of all classes that have been mixed into the
object named object.
-
info object namespace object
- This subcommand returns the name of the internal namespace of the object named
object.
-
info object variables object
- This subcommand returns a list of all variables that have been declared for
the object named object (i.e. that are automatically present in the
object's methods).
-
info object vars object ?pattern?
- This subcommand returns a list of all variables in the private namespace of
the object named object. If the optional pattern argument is
given, it is a filter (in the syntax of a string match glob pattern)
that constrains the list of variables returned. Note that this is different
from the list returned by info object variables; that can include
variables that are currently unset, whereas this can include variables that
are not automatically included by any of object's methods (or those of
its class, superclasses or mixins).
This command prints out a procedure suitable for saving in a Tcl
script:
proc printProc {procName} {
set result [list proc $procName]
set formals {}
foreach var [info args $procName] {
if {[info default $procName $var def]} {
lappend formals [list $var $def]
} else {
# Still need the list-quoting because variable
# names may properly contain spaces.
lappend formals [list $var]
}
}
puts [lappend result $formals [info body $procName]]
}
Every object necessarily knows what its class is; this information is
trivially extractable through introspection:
oo::class create c
c create o
puts [info object class o]
-> prints "::c"
puts [info object class c]
-> prints "::oo::class"
The introspection capabilities can be used to discover what class implements a
method and get how it is defined. This procedure illustrates how:
proc getDef {obj method} {
foreach inf [info object call $obj $method] {
lassign $inf calltype name locus methodtype
# Assume no forwards or filters, and hence no $calltype
# or $methodtype checks...
if {$locus eq "object"} {
return [info object definition $obj $name]
} else {
return [info class definition $locus $name]
}
}
error "no definition for $method"
}
This is an alternate way of looking up the definition; it is implemented by
manually scanning the list of methods up the inheritance tree. This code
assumes that only single inheritance is in use, and that there is no complex
use of mixed-in classes (in such cases, using info object call as above
is the simplest way of doing this by far):
proc getDef {obj method} {
if {$method in [info object methods $obj]} {
# Assume no forwards
return [info object definition $obj $method]
}
set cls [info object class $obj]
while {$method ni [info class methods $cls]} {
# Assume the simple case
set cls [lindex [info class superclass $cls] 0]
if {$cls eq ""} {
error "no definition for $method"
}
}
# Assume no forwards
return [info class definition $cls $method]
}
global(n), oo::class(n), oo::define(n), oo::object(n), proc(n), self(n)
command, information, interpreter, introspection, level, namespace, object, procedure, variable